Electrostatic chuck

ABSTRACT

One object of the present invention is to provide an electrostatic chuck which allows sufficiently rapid temperature rising/dropping thereof, in case that the diameter of a ceramic substrate is 190 mm or more or especially incase that the diameter of the ceramic substrate is quite large, exceeding 300 mm. The present invention discloses an electrostatic chuck comprising: a ceramic substrate equipped with a temperature controlling means; an electrostatic electrode formed on the ceramic substrate; and a ceramic dielectric film provided on the electrostatic electrode, wherein: the ceramic substrate has a diameter exceeding 190 mm and a thickness of 20 mm or less; and the ceramic dielectric film contains oxygen in an amount of 0.1 to 20 weight %.

TECHNICAL FIELD

[0001] The present invention relates to an electrostatic chuck usedmainly in the semiconductor industry, and particularly to anelectrostatic chuck which is thin, has small heat capacity and isexcellent in the temperature rising/dropping property.

BACKGROUND ART

[0002] Semiconductors are very important products necessitated byvarious industries. Semiconductor chips are produced, for example, byfirst preparing a silicon wafer by slicing silicon single crystal at apredetermined thickness and then forming a plurality of integratedcircuits and the like on the silicon wafer.

[0003] In the production process of semiconductor chips as describedabove, a semiconductor wafer such as a silicon wafer and the like is seton a device which allows various types of processing of thesemiconductor wafer, and subjected to various types of processingincluding etching, CVD and the like, whereby integrated circuits,elements and the like are formed thereon.

[0004] When a semiconductor wafer is subjected to such processing, thesemiconductor wafer must be firmly fixed to the device. For this reason,an electrostatic chuck inside of which electrostatic electrodes forattracting and firmly holding a semiconductor wafer are provided isgenerally employed.

[0005] As materials for constituting an electrostatic chuck, oxideceramics such as alumina or nitride ceramics are used. In the case of anelectrostatic chuck using ceramics as described above, electrostaticelectrodes are formed on a ceramic substrate and a thin dielectric filmis formed on each electrostatic electrode, so that the semiconductorwafer is adsorbed to the ceramic substrate by Coulomb force through thedielectric film. the semiconductor wafer needs to be heated, theelectrostatic chuck is generally provided with a means for heating theceramic substrate, such as a resistance heating element and the like.

[0006] In the electrostatic chuck using ceramics as described above, asYoung's modulus (strength) thereof is relatively large even at a hightemperature, the thickness of the ceramic substrate can be maderelatively thin and thus the weight of the electrostatic chuck can becharacteristically reduced.

SUMMARY OF THE INVENTION

[0007] However, in recent years, as the size of semiconductor waferbecomes larger and the area of a ceramic substrate inevitably increases,the heat capacity of electrostatic chuck is getting higher. As a result,the temperature of a ceramic substrate is less likely to promptly followthe change in the voltage or current amount and the rate of temperaturerising/dropping is slowed, whereby there arose a problem that theproductivity of semiconductor wafers and the like is deteriorated.

[0008] Further, when a ceramic substrate of a relatively large sizewhose diameter exceeds 300 mm is used in order to adapt to asemiconductor wafer of 12 inches, the temperature tends to dropexceedingly at the periphery of the ceramic substrate, whereby therearose a problem that the temperature distribution on the heating face ofthe ceramic substrate is not even.

[0009] The present invention has been contrived in order to solve theabove-mentioned problems. That is, one object of the present inventionis to provide an electrostatic chuck which allows sufficiently rapidtemperature rising/dropping thereof, in case that the diameter of aceramic substrate exceeds 190 mm, or especially even in case that thediameter of the ceramic substrate is quite large, exceeding 300 mm.

[0010] As a result of the assiduous study for achieving theabove-mentioned object, the inventors of the present invention havediscovered that the temperature rising/dropping properties of a ceramicsubstrate can be prevented from deteriorating by reducing the thicknessof the ceramic substrate to 20 mm or less and also reducing the heatcapacity of the ceramic substrate. The present invention has beencompleted on the basis of this discovery.

[0011] That is, in a first aspect of the present invention, anelectrostatic chuck comprises: a ceramic substrate equipped with atemperature controlling means; an electrostatic electrode formed on theceramic substrate; and a ceramic dielectric film provided on theabove-mentioned electrostatic electrode, wherein: the above-mentionedceramic substrate has a diameter exceeding 190 mm and a thickness of 20mm or less; and the above-mentioned ceramic dielectric film containsoxygen in an amount of 0.1 to 20 weight %.

[0012] According to the electrostatic chuck of the first aspect of thepresent invention, by reducing the thickness of the ceramic substrate to20 mm or less, the temperature dropping at the peripheral portion of theceramic substrate can be made as small as possible and the heat capacitythereof can be made small, even in case that the ceramic substrate has arelatively large size and the diameter thereof exceeds 190 mm. As aresult, an electrostatic chuck which allows rapid temperaturerising/dropping thereof can be realized.

[0013] When a ceramic substrate has a relatively large diameter, theceramic substrate tends to deflect due to its own weight and thus aclearance is likely to be generated between the semiconductor wafer andthe ceramic substrate, whereby heating of the semiconductor wafer evenlybecomes difficult to be performed. Also, the thinner the substrate is,the more the substrate deflects.

[0014] However, in the above-mentioned ceramic dielectric film, as thedielectric film contains oxygen in an amount of 0.1 to 20 weight %,rigidity of the dielectric film is improved so that the magnitude offlexure can be reduced.

[0015] In the electrostatic chuck of the first aspect of the presentinvention, it is preferable to use a resistance heating element as theabove-mentioned temperature controlling means, because a resistanceheating element can be formed In the electrostatic chuck relativelyeasily by: coating a conductor containing paste to a green sheet or asintered body and subjecting the resultant to heating and firing; orembedding a metal wire in a formed body and subjecting the resultant tofiring.

[0016] In a second aspect of the present invention, an electrostaticchuck comprises: a ceramic substrate equipped with a temperaturecontrolling means; an electrostatic electrode formed on the ceramicsubstrate; and a ceramic dielectric film provided on the above-mentionedelectrostatic electrode, wherein the above-mentioned ceramic substratehas a diameter exceeding 300 mm and a thickness of 20 mm or less.

[0017] In a case of a large type ceramic substrate whose diameterexceeds 300 mm, the area of the side face of the periphery thereof isrelatively large and heat is easily lost there by being brought intocontact with air. As a result, the temperature drop at the periphery ofthe ceramic substrate is large.

[0018] However, in the electrostatic chuck of the second aspect of thepresent invention, the thickness of the substrate is adjusted to 20 mmor less so that the contact area where the side face of the substrate isbrought into contact with air decreases and heat is less likely to bereleased there and hence the temperature dropping at the peripheralportion can be made small. Also, the thickness of the substrate isadjusted to 20 mm or less so that the heat capacity thereof is madesmall. Thus, an electrostatic chuck which makes rapid temperaturerising/dropping thereof possible is realized.

[0019] In the electrostatic chuck of the second aspect of the presentinvention, the above-mentioned ceramic dielectric film preferablycontains oxygen in an amount of 0.1 to 20 weight %.

[0020] In case that the diameter of a ceramic substrate exceeds 300 mm,when the thickness of the substrate is made 20 mm or less, the ceramicsubstrate tends to deflect due to its own weight and thus a clearance islikely to be generated between the semiconductor wafer and the ceramicsubstrate, whereby even heating of the semiconductor wafer may becomedifficult to be performed and/or the chucking force may undesirablydisperse. However, by setting the content of oxygen in the ceramicdielectric film in a range of 0.1 to 20 weight %, rigidity of thesubstrate is improved and thus the magnitude of flexure can be reduced.

[0021] Further, in the electrostatic chuck of the second aspect of thepresent invention, it is preferable to use a resistance heating elementas the above-mentioned temperature controlling means, because aresistance heating element can be formed in the electrostatic chuckrelatively easily by: coating a conductor containing paste to a greensheet or a sintered body and subjecting the resultant to heating andfiring; or embedding a metal wire in a formed body and subjecting theresultant to firing.

[0022] Yet further, in the electrostatic chuck of the second aspect ofthe present invention, the thickness of the above-mentioned ceramicdielectric film is preferably in a range of 50 to 5000 μm. When thethickness of the ceramic dielectric film is within in theabove-mentioned range, the magnitude of flexure of the ceramic substratecan be reduced.

[0023] Incidentally, the publication of JP Kokai Hei 4-304942 disclosesan electrostatic chuck which comprises a ceramic substrate whosethickness is 10 mm and diameter is 150 mm. However, in the case of thisreference, the problem which the present invention tries to solve doesnot occur at all because the diameter of the substrate is quite small.

[0024] Also, the publication of JP Kokai Hei 7-86379 discloses anelectrostatic chuck which includes a ceramic substrate whose thicknessis 5 mm and diameter is 210 mm. However, in the case of this reference,the ceramic substrate thereof does not have sufficient rigidity becausethe content of yttria in the substrate is 2 weight % and this is small.As a result, the chucking force disperses in the electrostatic chuck.

[0025] Further, the publication of JP Kokai Hei 10-72260 discloses aceramic substrate whose diameter is 200 mm and thickness is 12 mm.However, this reference makes no description of the oxygen content ofthe ceramic substrate.

[0026] In short, the above-mentioned references of the prior art are allrelated to a substrate whose diameter is smaller than 300 mm andirrelevant to the problem of temperature dropping at the periphery ofthe substrate.

BRIEF DESCRIPTION OF DRAWINGS

[0027]FIG. 1 is a longitudinal sectional view which schematically showsone example of an electrostatic chuck according to the first and thesecond aspects of the present invention.

[0028]FIG. 2 is a sectional view taken along the A-A line of theelectrostatic chuck shown in FIG. 1.

[0029]FIG. 3 is a sectional view taken along the B-B line of theelectrostatic chuck shown in FIG. 1.

[0030]FIG. 4 is a longitudinal sectional view which schematically showsone example of an electrostatic chuck according to the first and thesecond aspects of the present invention.

[0031]FIG. 5 is a longitudinal sectional view which schematically showsone example of an electrostatic chuck according to the first and thesecond aspects of the present invention.

[0032]FIG. 6 is a longitudinal sectional view which schematically showsone example of an electrostatic chuck according to the first and thesecond aspects of the present invention.

[0033] FIGS. 7(a) to 7(d) are longitudinal sectional views whichschematically shows some steps of the production process of anelectrostatic chuck according to the first and the second aspects of thepresent invention.

[0034]FIG. 8 is a horizontal sectional views schematically showing oneexample of electrostatic electrodes which constitute an electrostaticchuck according to the first and the second aspects of the presentinvention.

[0035]FIG. 9 is a horizontal sectional views schematically showing oneexample of electrostatic electrodes which constitute an electrostaticchuck according to the first and the second aspects of the presentinvention.

[0036]FIG. 10 is a sectional views which schematically shows anelectrostatic chuck according to the first and the second aspects of thepresent invention in a state in which the electrostatic chuck is fixedin a supporting case.

EXPLANATION OF NUMERALS

[0037]  2, 22, 32a, 32b chuck positive electrostatic layer  2a, 3asemicircular arc part  2b, 3b combteeth-shaped part  3, 23, 33a, 33bchuck negative electrostatic layer  4 ceramic dielectric film  5resistance heating element  6 external terminal pin  7 metal wire  8Peltier device  9 silicon wafer 11 bottomed hole 12 through hole 15resistance heating element 16, 17 conductor-filled through hole 20, 30,101 electrostatic chuck 41 supporting case 42 coolant outlet 43inhalation duct 44 coolant inlet 45 heat insulator 81 thermocouple 82ceramic substrate

DETAILED DESCRIPTION OF THE INVENTION

[0038] First, an electrostatic chuck according to the first aspect ofthe present invention will be described with reference to the drawings.

[0039] In the first aspect of the present invention, an electrostaticchuck comprises: a ceramic substrate equipped with a temperaturecontrolling means; an electrostatic electrode formed on the ceramicsubstrate; and a ceramic dielectric film provided on the above-mentionedelectrostatic electrode, wherein: the above-mentioned ceramic substratehas a diameter exceeding 190 mm and a thickness of 20 mm or less; andthe above-mentioned ceramic dielectric film contains oxygen in an amountof 0.1 to 20 weight %.

[0040]FIG. 1 is a longitudinal sectional view which schematically showsone embodiment of an electrostatic chuck according to the first aspectof the present invention. FIG. 2 is a sectional view taken along the A-Aline of the electrostatic chuck shown in FIG. 1. FIG. 3 is a sectionalview taken along the B-B line of the electrostatic chuck shown in FIG.1.

[0041] In this electrostatic chuck 101, a chuck positive electrostaticlayer 2 having a semicircular arc part 2 a and a combteeth-shaped part 2b and a chuck negative electrostatic layer 3 having a semicircular arcpart 3 a and a combteeth-shaped part 3 b are formed on the surface of adisc-shaped ceramic substrate 1 in the manner that the two electrostaticlayers face each other and the combteeth-shaped portion 2 b and thecombteeth-shaped portion 3 b cross each other. A thin ceramic dielectricfilm 4 is further formed on the ceramic substrate 1 which contains theelectrostatic electrodes.

[0042] The chuck positive electrostatic layer 2 and the chuck negativeelectrostatic layer 3 are connected to the positive side and thenegative side of a direct power source, respectively, so that a directcurrent voltage V₂ is applied thereto. A silicon wafer 9 is set on thiselectrostatic chuck 101 and grounded.

[0043] On the other hand, a resistance heating element 5 havingconcentric circles-like shape as shown in FIG. 3 as viewed from theabove is provided inside the ceramic substrate 1, so that thetemperature of the silicon wafer 9 is controlled by the resistanceheating element 5. An external terminal pin 6 is connected and fixed toeach end of the resistance heating element 5, so that a voltage V₁ isapplied to each end of the resistance heating element 5. Further,although not shown in FIGS. 1 and 2, bottomed holes 11 to each of whicha temperature measuring element is inserted and through holes 12 througheach of which a lifter pin (not shown) for supporting and verticallymoving the silicon wafer 9 is inserted, are formed in the ceramicsubstrate 1. The resistance heating element 5 may be formed on thebottom face of the ceramic substrate.

[0044] In the above-mentioned structure, when a direct current voltageV₂ is applied between the chuck positive electrostatic layer 2 and thechuck negative electrostatic layer 3, the silicon wafer 9 is adsorbedand fixedly held by the ceramic dielectric film 4, due to theelectrostatic action (Coulomb force) between the chuck positiveelectrostatic layer 2 and the chuck negative electrostatic layer 3.

[0045] The diameter of the ceramic substrate which constitutes theelectrostatic chuck of the first aspect of the present invention exceeds190 mm, this is because the electrostatic chuck can cope with a siliconwafer of large size. The diameter of the above-mentioned ceramicsubstrate is preferably 200 mm or more, and more preferably larger than200 mm. It is especially preferable that the diameter of the ceramicsubstrate is 300 mm or larger, in terms of well coping with asemiconductor wafer of the next generation.

[0046] The thickness of the above-mentioned ceramic substrate is to be20 mm or less, and preferably 10 mm or less. This is to reduce the heatcapacity of the electrostatic chuck by making the electrostatic chuckthinner, to cope with the enlargement of the size of the electrostaticchuck. When the diameter of a ceramic substrate is 300 mm or more, thearea of the periphery becomes larger and thus the contact area at whichthe ceramic substrate is brought into contact with the atmospheric gassuch as air becomes larger, whereby the temperature significantly dropsat the peripheral portion of the substrate. Therefore, theabove-mentioned contact area is reduced by decreasing the thickness ofthe ceramic substrate, so that the temperature dropping at theperipheral portion is prevented.

[0047] Especially, by setting the thickness of the substrate to 10 mm orless, the temperature dropping property is improved. It is particularlypreferable that the thickness of the ceramic substrate is within a rangeof 1 to 5 mm because the dispersion of the temperature on the heatingface is decreased.

[0048] As described above, the ceramic dielectric film which constitutesthe electrostatic chuck of the first aspect of the present inventioncontains oxygen in an amount of 0.1 to 20 weight %.

[0049] The thinner the substrate is, the more the substrate deflects.However, by incorporating the oxygen in a range of 0.1 to 20 weight %,the rigidity of the substrate is improved and the magnitude of fluxurethereof can be decreased.

[0050] The electrostatic chuck of the first aspect of the presentinvention has the above-mentioned structure and is realized, forexample, in the embodiment as shown in FIGS. 1 to 3.

[0051] Hereinafter, each of the members which constitute theabove-mentioned electrostatic chuck, as well as other embodiments andthe like of the electrostatic chuck of the first aspect of the presentinvention, will be described one by one in detail.

[0052] The ceramic dielectric film which constitutes the electrostaticchuck of the first aspect of the present invention is provided in amanner that the electrostatic electrodes formed on the ceramic substrateare covered by the ceramic dielectric film.

[0053] The ceramic material which constitutes this ceramic dielectricfilm is not particularly restricted, and examples thereof includenitride ceramic, carbide ceramic, oxide ceramic and the like.

[0054] Examples of the above-mentioned nitride ceramic include metalnitride ceramic such as aluminum nitride, silicon nitride, boronnitride, titanium nitride and the like.

[0055] Examples of the above-mentioned carbide ceramic include metalcarbide ceramic such as silicon carbide, zirconium carbide, titaniumcarbide, tantalum carbide, tungsten carbide and the like.

[0056] Examples of the above-mentioned oxide ceramic include metal oxideceramic such as alumina, zirconia, cordierite, mullite and the like.

[0057] These examples of ceramic may be used solely or in a combinationof two or more of them.

[0058] Among these examples of ceramic, nitride ceramic and carbideceramic are more preferable than oxide ceramic because the thermalconductivity of nitride ceramic and that of carbide ceramic is higherthan that of oxide ceramic.

[0059] Among the examples of the nitride ceramic, aluminum nitride isthe most preferable because the thermal conductivity thereof, which is180 W/m·K, is the highest in the nitride ceramics.

[0060] It is preferable that the above-mentioned ceramic dielectric filmcontains oxygen in an amount of 0.1 to 20 weight %. When the content ofoxygen in the ceramic dielectric film is less than 0.1 weight %, asufficient breakdown voltage cannot be ensured. On the other hand, whenthe content of oxygen in the ceramic dielectric film exceeds 5 weight %,the breakdown voltage drops due to the deterioration of the highbreakdown voltage property of the oxides at a high temperature. Further,when the content of oxygen in the ceramic dielectric film exceeds 20weight %, the temperature rising/dropping property of the ceramicsubstrate deteriorates due to the drop in the thermal conductivity.

[0061] Firing is carried out: after heating the raw material powder ofthe nitride ceramic, the carbide ceramic and the like as described abovein the air or oxygen gas; or after mixing the above-mentioned rawmaterial powder with metal oxides, in order to incorporate oxygen in theabove-mentioned nitride ceramic or the carbide ceramic and the like.

[0062] Examples of the above-mentioned metal oxide include yttria(Y₂O₃), alumina (Al₂O₃), rubidium oxide (Rb₂O), lithium oxide (Li₂O),calcium carbonate (CaCO₃) and the like.

[0063] It is preferable that 1 to 20 parts by weight of the metal oxideas described above is added to 100 parts by weight of the nitrideceramic.

[0064] The above-mentioned dielectric film may be composed of siliconcarbide which contains B, C, Be, BeO and the like as the sintering aid,because such a dielectric film exhibits high mechanical strength andexcellent heat resistance.

[0065] The above-mentioned ceramic dielectric film desirably containscarbon. In case that the thermal conductivity of the ceramic dielectricfilm at a high temperature (approximately 500° C.) is to be preventedfrom decreasing, it is preferable that crystalline carbon is added tothe ceramic dielectric film. In case that the volume resistivity of theceramic dielectric film at a high temperature is to be prevented fromdecreasing, it is preferable that amorphous carbon is added to theceramic dielectric film. Accordingly, depending on the application, boththe volume resistivity and the thermal conductivity can besimultaneously adjusted in an appropriate manner by adding bothcrystalline carbon and amorphous carbon threto.

[0066] The crystallinity of carbon can be determined by analyzing themagnitude of peaks in the vicinities of 1550 cm⁻¹ and 1333 cm⁻¹ obtainedwhen Raman spectrum is measured.

[0067] When the ceramic dielectric film contains carbon, the content ofcarbon contained in the ceramic dielectric film is preferably in a rangeof 5 to 5000 ppm. When the content of carbon in the ceramic dielectricfilm is less than 5 ppm, radiant heat is decreased and there arisesdifficulty in concealing the electrostatic electrodes. On the otherhand, when the content of carbon in the ceramic dielectric film exceeds5000 ppm, the ceramic dielectric film can no longer be made dense andthere arises difficulty in suppressing drop in the volume resistivityThe content of carbon in the ceramic dielectric film is most preferablyin a range of 100 to 2000 ppm.

[0068] In order to make the carbon contained in the ceramic dielectricfilm into amorphous one, a resin or hydrocarbons and the like which areless likely to become crystalline by heating may be added at the time ofproducing a formed body by mixing the raw material powder, a resin, asolvent and the like together, thus the formed body is degreased in anatmosphere which contains relatively little oxygen or a non-oxidizingatmosphere. Alternatively, it is acceptable to produce amorphous carbonby heating a hydrocarbon such as saccharose and the like or a resinwhich are easily made amorphous by heating and then adding the obtainedamorphous carbon to the ceramic dielectric film. In case thatcrystalline carbon is to be added to the ceramic dielectric film,graphite which has been made powdery by pulverizing or crystallinecarbon black can be used.

[0069] Further, as the decomposing rate of an acrylic resin bindervaries depending on the acid value thereof, it is possible to adjust theamount of carbon or crystallinity, to some extent, by changing the acidvalue of the acrylic resin binder.

[0070] The thickness of the above-mentioned ceramic dielectric film ispreferably in a range of 50 to 5000 μm. When the thickness of theabove-mentioned ceramic dielectric film is less than 50 μm, a sufficientbreakdown voltage cannot be obtained because the dielectric film is toothin, whereby there is a possibility that the ceramic dielectric filmsuffers from dielectric breakdown when a silicon wafer is set andadsorbed thereon. In addition, when the thickness of the ceramicdielectric film is less than 50 μm, the stiffness of the ceramicdielectric film is not sufficient, whereby fluxure of theabove-mentioned ceramic substrate cannot be prevented. On the otherhand, when the thickness of the ceramic dielectric film exceeds 5000 μm,the distance between the silicon wafer and the electrostatic electrodesis so large that the capacity of attracting the silicon wafer isdeteriorated. Accordingly, the thickness of the ceramic dielectric filmis more preferably in a range of 50 to 1500 μm.

[0071] It is preferable that the porosity of the above-mentioned ceramicdielectric film is 5% or less and the diameter of the largest pore is 50μm or less.

[0072] When the above-mentioned porosity exceeds 5%, the number of thepores present in the ceramic dielectric film increases and the diameterof the pores becomes too large. As a result, the pores are likely tocommunicate with each other and the breakdown voltage tends to drop inthe ceramic dielectric film of such a structure.

[0073] On the other hand, when the diameter of the largest pore exceeds50 μm, the ratio of the pore diameter with respect to the thickness ofthe ceramic dielectric film, as well as the proportion of the poreswhich are communicated with each other, is increased, whereby thebreakdown voltage tends to drop.

[0074] The porosity is more preferably 0, or 3% or less and the diameterof the largest pore is more preferably 0, or 10 μm or less.

[0075] The porosity and the diameter of the largest pore are adjusted bythe length of pressurizing time, the pressure, the temperature duringthe sintering process and the amount of the additives such as SiC, BN.SiC or BN inhibits the sintering process, thereby facilitatingintroduction of pores to the ceramic dielectric film.

[0076] Measurement of the diameter of the largest pore is carried outby: preparing five samples; grinding the surface of each sample into themirror plane; photographing the surface of each sample at ten sites byan electron microscope with 2000 to 5000 magnifications; measuring thediameter of the largest pore in each shot; and calculating the averageof the diameters of the largest pores of 50 shots.

[0077] The porosity is measured by Archimedes' method which includes thesteps of: pulverizing the sintered body; mixing the pulverized materialwith an organic solvent or mercury and measuring the volume of thepulverized material; obtaining the true specific gravity of thepulverized material from the weight and the volume of the pulverizedmaterial; and calculating the porosity from the true specific gravityand the apparent gravity of the sintered body.

[0078] The ceramic dielectric film may include pores to some extent asdescribed above, because the presence of an acceptable number of openpores at the surface of the ceramic dielectric film facilitates smoothdechucking.

[0079] Examples of the electrostatic electrodes formed on the ceramicsubstrate include a sintered body of metal or conductive ceramic, metalfoils and the like. The metal sintered body is preferably made of atleast one kind of metal selected from tungsten and molybdenum. The metalfoils are preferably made of the same material as the metal sinteredbody, because these metals are relatively less likely to be oxidized andhave sufficient conductivity as an electrode. As the conductive ceramic,at least one kind selected from the group consisting of carbide oftungsten and carbide of molybdenum can be used.

[0080] Examples of the material of the ceramic substrate used in theelectrostatic chuck of the first aspect of the present invention includenitride ceramic, carbide ceramic, oxide ceramic and the like.

[0081] Examples of the above-mentioned nitride ceramic, theabove-mentioned carbide ceramic and the above-mentioned oxide ceramic asthe material of the ceramic substrate include those raised in thedescription of the above-mentioned ceramic dielectric film.

[0082] Among these examples of ceramic described above, nitride ceramicand carbide ceramic are preferable because nitride ceramic and carbideceramic have relatively high thermal conductivity and thus canexcellently conduct the heat generated at the resistance heatingelement.

[0083] It is preferable that the ceramic dielectric film and the ceramicsubstrate are made from the same materials, because in such a case, theproduction process of the electrostatic chuck can be easily carried outby laminating green sheets produced by the same method and firing thelamination in the same condition.

[0084] Among the examples of nitride ceramic, aluminum nitride is themost preferable because the thermal conductivity thereof, which is 180W/m·K, is the highest in the nitride ceramics.

[0085] The above-mentioned ceramic substrate may include carbon becausecarbon contributes to generation of high radiation heat. The content ofcarbon in the ceramic substrate is preferably in a range of 5 to 5000ppm.

[0086] Carbon may be either in the crystalline state, for example in theform of graphite powder, or in the amorphous state as is achieved byusing a hydrocarbon or a resin which are easily made amorphous.Alternatively, both of carbon in the crystalline state and carbon in theamorphous state may be used together.

[0087] The ceramic such as nitride ceramic which constitutes the ceramicsubstrate preferably contains 0.1 to 20 weight % of metal oxidestherein, as is the case with the ceramic dielectric film.

[0088] It is preferable that the porosity of the above-mentioned ceramicsubstrate is 5% or less and the diameter of the largest pore is 50 μm orless. Further, the porosity is more preferably 0, or 3% or less and thediameter of the largest pore is 0, or 10 μm or less.

[0089]FIGS. 8 and 9 are horizontal sectional views schematically showingelectrostatic electrodes in other types of electrostatic chuck. In theelectrostatic chuck 20 shown in FIG. 8, a chuck positive electrostaticlayer 22 and a chuck negative electrostatic layer 23 each having asemicircular shape are formed inside the ceramic substrate 1. In theelectrostatic chuck shown in FIG. 9, a chuck positive electrostaticlayer 32 a, 32 b and a chuck negative electrostatic layer 33 a, 33 beach having a form obtained by equally dividing a circle into fourportions, are formed inside the ceramic substrate 1. The two chuckpositive electrostatic layers 22 a, 22 b and two chuck negativeelectrostatic layer 33 a, 33 b are formed, such that the two chuckpositive electrostatic layers 22 a, 22 b and the two chuck negativeelectrostatic layers 33 a, 33 b intersect each other.

[0090] The electrostatic chuck may be provided with RF electrodes, andthe electrostatic electrodes may be provided on the both faces of theceramic substrate.

[0091] In case that the electrostatic electrodes are formed such thatthe electrostatic electrodes have shapes which would be obtained bydividing a circular electrode into plural pieces, the number of thedivided pieces is not particularly restricted and may be five or more,and the shape of the divided pieces is not restricted to a sector form,either.

[0092] In the electrostatic chuck according to the first aspect of thepresent invention, a temperature controlling means such as a resistanceheating element is provided, as shown in FIG. 1. The temperaturecontrolling means is provided, because tasks such as heating the siliconwafer set on the electrostatic chuck are required during the CVDprocessing and the like.

[0093] Examples of the above-mentioned temperature controlling meansinclude a Peltier device (refer to FIG. 6), in addition to theresistance heating element 5 shown in FIG. 3. The resistance heatingelement may be provided either inside the ceramic substrate or on thebottom face of the ceramic substrate. In case that the resistanceheating element is provided in the ceramic substrate, a coolant (such asair) outlet and the like as a cooling means may be provided in thesupporting case in which the electrostatic chuck is fitted.

[0094] In case that the resistance heating element is provided insidethe ceramic substrate, the resistance heating element may be provided inthe form of a plurality of layers. In this case, it is preferable thatthe patterns at the layers are formed so that the patterns complementeach other, whereby any portion of the heating face is covered by one ofthese patterns or layers without leaving any uncovered portion whenviewed from the above. For example, a structure having a staggeredarrangement may be used.

[0095] In case that the resistance heating element is set in the ceramicsubstrate, it is preferable that the resistance heating element isprovided at a position which is within 60% of the ceramic substratethickness as measured from the bottom face of the ceramic substrate, sothat heat is well dissipated before reaching the heating face and thedistribution of the temperature on the heating face is reliably madeeven.

[0096] Examples of the resistance heating element include a sinteredbody of metal or conductive ceramic, a metal foil, a metal wire and thelike. As the metal sintered body, a metal sintered body which isproduced by using at least one kind of element selected from tungstenand molybdenum is preferable, because these metals are relatively lesslikely to be oxidized and have a sufficient resistance value forgenerating heat.

[0097] As the conductive ceramic, at least one kind selected fromcarbides of tungsten and molybdenum can be preferably used.

[0098] Further, in case that the resistance heating element is formed onthe bottom face of the ceramic substrate, it is preferable to use raremetal (gold, silver, palladium, platinum) or nickel for the metalsintered body. Specifically, silver, silver-palladium can be preferablyused.

[0099] The shape of the metal particles used for producing theabove-mentioned metal sintered body may be either spherical or scaly. Incase that these metal particles are used, both spherical particles andscaly particles may be used in a mixed manner.

[0100] A metal oxide may be added to the metal sintered body. Theabove-mentioned metal oxide is used in order to tightly adhere the metalparticles to the ceramic substrate. The reason why the above-mentionedmetal oxide improves the adhesion of the metal particles to the ceramicsubstrate is not clearly known. But, a thin oxidized film is formed onthe surface of the metal particle, and an oxidized film is also formedon the surface of the ceramic substrate, regardless of whether theceramic substrate is oxide ceramic or non-oxide ceramic. It is thusassumed that the oxidized film of the metal particle and that of theceramic substrate are combined to one film through the metal oxide whenthese oxidized films are sintered on the surface of the ceramicsubstrate, whereby the metal particles are closely adhered to theceramic substrate.

[0101] As the above-mentioned metal oxide, at least one kind of compoundselected from the group consisting of lead oxide, zinc oxide, silica,boron oxide (B₂O₃), alumina, yttria and titania is preferably used,because these oxides can improve adhesion of the metal particles to theceramic substrate without increasing the resistance value of theresistance heating element.

[0102] The content of the metal oxide is preferably in a range of 0.1parts by weight or more and less than 10 parts by weight with respect to100 parts by weight of the metal particles. By using the metal oxidewithin the above-mentioned range, the adhesion between the metalparticles and the ceramic substrate can be enhanced without increasingthe resistance value too much.

[0103] The contents of lead oxide, zinc oxide, silica, boron oxide(B₂O₃), alumina, yttria and titania are preferably 1 to 10 parts byweight of lead oxide, 1 to 30 parts by weight of silica, 5 to 50 partsby weight of boron oxide, 20 to 70 parts by weight of zinc oxide, 1 to10 parts by weight of alumina, 1 to 50 parts by weight of yttria and 1to 50 parts by weight of titania, with respect to the whole weight ofthe metal oxides expressed as 100 parts by weight. However, it ispreferable that these contents of the metal oxides are adjusted so thatthe total sum of the metal oxides does not exceed 100 parts by weight,because these metal oxides can especially enhance adhesion thereof tothe ceramic substrate in such a range.

[0104] In case that the resistance heating element is provided on thebottom face of the ceramic substrate, the surface of the resistanceheating element 15 is preferably covered with a metal layer 150 (referto FIG. 4). As the resistance heating element 15 is a sintered body ofmetal particles, the resistance heating element 15 is easily oxidized ifit is exposed, and the resistance value thereof changes due to thisoxidization. By covering the surface of the resistance heating element15 with a metal layer 150, such oxidization can be prevented.

[0105] The thickness of the metal layer 150 is preferably in a range of0.1 to 10 μm. When the thickness of the metal layer is within thisrange, the oxidization of the resistance heating element can beprevented without changing the resistance value of the resistanceheating element.

[0106] The metal used for the metal layer for covering is notparticularly limited, as long as the metal is non-oxidizable. Specificexamples thereof include at least one element selected from the groupconsisting of gold, silver, palladium, platinum and nickel. Among theseexamples, nickel is more preferable. The resistance heating elementrequires a terminal for connecting itself to the power source, and thisterminal is mounted to the resistance heating element by using solder.Nickel effectively prevents the heat dissipation caused by solder. Asthe connection terminal, a terminal pin made of Kovar can be used.

[0107] In case that the resistance heating element is formed inside theceramic substrate, the surface of the resistance heating element is notoxidized and thus no covering by the metal layer is required. When theresistance heating element is formed inside the ceramic substrate, aportion of the surface of the resistance heating element may be exposedoutside of the ceramic substrate.

[0108] In case that the ceramic substrate is produced by: fillingceramic powder and the like in a mold; producing a formed body; andfiring the obtained formed body thereafter, the resistance heatingelement can be disposed by embedding a metal foil or a metal wire in theformed body.

[0109] Preferable examples of the metal foil used as the resistanceheating element include a resistance heating element produced byconducting a pattern-forming process (such as etching) to nickel foil orstainless foil.

[0110] The metal foils which have been subjected to the pattern-formingprocess may be laminated with a resin film and the like.

[0111] Example of the metal wire include a tungsten wire, a molybdenumwire and the like.

[0112] In case that the Peltier device is used as the temperaturecontrolling means, either heating or cooling can be performed by thesame element by changing the flow direction of the current, which isadvantageous.

[0113] The Peltier device 8 is formed by connecting p-type and n-typethermoelectric elements 81 in series and attaching these thermoelectricelements 81 to a ceramic plate 82 and the like, as shown in FIG. 6.

[0114] Examples of the Peltier device include the silicon/germanium-typePeltier device, the bismuth/antimony-type Peltier device, thelead/tellurium-type Peltier device and the like.

[0115] Examples of the electrostatic chuck according to the first aspectof the present invention include: an electrostatic chuck 101 having astructure in which, as shown in FIG. 1, the chuck positive electrostaticlayer 2 and the chuck negative electrostatic layer 3 are formed betweenthe ceramic substrate 1 and the ceramic dielectric film 4 and theresistance heating element 5 is provided inside the ceramic substrate 1;an electrostatic chuck 201 having a structure in which, as shown in FIG.4, the chuck positive electrostatic layer 2 and the chuck negativeelectrostatic layer 3 are formed between the ceramic substrate 1 and theceramic dielectric film 4 and the resistance heating element 15 isprovided on the bottom face of the ceramic substrate 1; an electrostaticchuck 301 having a structure in which, as shown in FIG. 5, the chuckpositive electrostatic layer 2 and the chuck negative electrostaticlayer 3 are formed between the ceramic substrate 1 and the ceramicdielectric film 4 and a metal wire 7 as a resistance heating element isembedded inside the ceramic substrate 1; and an electrostatic chuck 401having a structure in which, as shown in FIG. 6, the chuck positiveelectrostatic layer 2 and the chuck negative electrostatic layer 3 areformed between the ceramic substrate 1 and the ceramic dielectric film 4and a Peltier device 8 composed of a thermoelectric element 81 and aceramic plate 82 is formed on the bottom face of the ceramic substrate1; and the like.

[0116] In the first aspect of the present invention, as shown in FIGS. 1to 5, the chuck positive electrostatic layer 2 and the chuck negativeelectrostatic layer 3 are provided between the ceramic substrate 1 andthe ceramic dielectric film 4, and the resistance heating element 5 andthe metal wire 7 are formed inside the ceramic substrate 1. As a result,connecting portions (conductor-filled through holes) 16, 17 forconnecting these with the external terminals, are required. Theconductor-filled through holes 16, 17 are formed by filling a metalhaving a high melting point such as tungsten paste and molybdenum pasteor a conductive ceramic such as tungsten carbide and molybdenum carbide.

[0117] Here, the diameter of the connecting portions (conductor-filledthrough holes) 16, 17 is preferably in a range of 0.1 to 10 mm, becausewhen the diameter of the connecting portions is within this range, notonly occurrence of disconnection of the wires but also generation ofcracks or strains can be prevented.

[0118] External terminals 6, 18 are connected thereto, by using theconductor-filled through holes as connection pads (refer to FIG. 7(d)).

[0119] Such connection is performed by using solder or brazing fillermetal. As the brazing filler metal, silver braze, palladium braze,aluminum braze and gold braze are preferable. As the gold braze, Au—Nialloy is preferable because Au—Ni alloy exhibits excellent adhesionproperty to tungsten.

[0120] The ratio of Au/Ni is preferably [81.5 to 82.5 (weight %)]/[18.5to 17.5 (weight %)].

[0121] The thickness of the Au—Ni layer is preferably in a range of 0.1to 50 μm, because the connection property is reliably obtained when thethickness of the Au—Ni layer is within this range. In the case of Au—Cualloy, the alloy exhibits deterioration when used in a highly vacuumedstate of 10⁻⁶ to 10⁻⁵ Pa at a high temperature in a range of 500 to1000° C. On the other hand, the Au—Ni alloy does not exhibitdeterioration when the alloy is used in such a harsh condition, which isadvantageous. The content of the impurity elements contained in theAu—Ni alloy is preferably less than 1 parts by weight when the wholeweight of the Au—Ni alloy is expressed as 100 parts by weight.

[0122] In the first aspect of the present invention, a thermocouple maybe embedded in the bottomed hole 12 of the ceramic substrate 1,according to necessity. In this arrangement, the temperature of theresistance heating element can be measured by the thermocouple, so thatthe temperature of the resistance heating element can be controlled bychanging the voltage and the current amount on the basis of the obtaineddata.

[0123] The size of the connecting portion of the metal wire of thethermocouple is preferably the same as or larger than the stranddiameter of each metal wire, but 0.5 mm or less. The heat capacity ofthe connecting portion is made small by such a structure, whereby thetemperature is converted into correctly and rapidly into the currentvalue. As a result, the temperature controlling property is improved,whereby the temperature distribution on the heating face of the wafer iskept small.

[0124] Examples of the above-mentioned thermocouple include the K-type,the R-type, the B-type, the S-type, the E-type, the J-type and theT-type thermocouples, as are raised in JIS-C-1602 (1980).

[0125]FIG. 10 is a sectional view which schematically shows a supportingcase 41 in which the electrostatic chuck having a structure as describedabove according to the first aspect of the present invention is fitted.

[0126] The supporting case 41 is designed such that the electrostaticchuck 101 is fitted therein through a heat insulator 45. In thesupporting case 41, coolant outlets 42 are formed such that the coolantintroduced from a coolant inlet 44 is discharged outside from aninhalation duct 43 through the coolant outlet 42. By the action of thiscoolant, the electrostatic chuck 101 can be cooled.

[0127] The supporting case may be structured such that the ceramicsubstrate, which has been set on the upper surface of the supportingcase, is fixed to the supporting case by the fixing member like bolts.

[0128] The electrostatic chuck according to the first aspect of thepresent invention is preferably used in a temperature range of 100 to800° C.

[0129] Next, one example of the method of producing the electrostaticchuck according to the first aspect of the present invention will bedescribed with reference to the sectional views shown in FIGS. 7(a) to(d).

[0130] (1) First, a green sheet 50 is produced by: preparing powder ofceramic such as oxide ceramic, nitride ceramic and carbide ceramic,(powder of nitride or carbide ceramic is fired in an oxidizingatmosphere so that the ceramic powder contains oxygen) mixing theceramic powder with an auxiliary agent, a binder, a solvent and thelike, thereby preparing a paste; and forming the paste in a sheet-likeform by the doctor blade method and the like, thereby producing a greensheet 50.

[0131] As the above-mentioned ceramic powder, aluminum nitride, siliconcarbide and the like may be used, for example. Further, a sintering aidsuch as yttria and carbon may further be added thereto, according tonecessity.

[0132] One or plurality of the green sheet 50, which is laminated on thegreen sheet having an electrostatic electrode layer printed body 51formed thereon, described below, is the layer which serves as theceramic dielectric film 4.

[0133] In general, it is preferable that the same raw material is usedfor the ceramic dielectric film 4 and the ceramic substrate 1, becausethen the same preferable firing conditions can be applied to both theceramic dielectric film 4 and the ceramic substrate 1 during the firingprocess thereof since normally, the ceramic dielectric film 4 and theceramic substrate 1 are sintered together in the integrated arrangement.In case that different raw materials are used for the ceramic dielectricfilm 4 and the ceramic substrate 1, the ceramic substrate may beproduced first, so that the electrostatic electrode layer is formedthereon and the ceramic dielectric film is further provided on theelectrostatic electrode layer.

[0134] Examples of the binder which is generally used for the productionof an electrostatic chuck include an acrylic binder, an ethyl cellulose,a butyl cellosolve and polyvinyl alcohol and the like. At least one kindof binder selected from the above-mentioned group can be used as thebinder for forming the ceramic subsrate.

[0135] As the solvent, at least one kind of solvent selected fromα-terpineol and glycol is preferably used.

[0136] A through hole which a lifter pin of the silicon wafer is pushedthrough and a concave portion in which thermocouple is embedded may beoptionally formed in the green sheet 50. The through hole and theconcave portion can be formed by punching and the like.

[0137] The thickness of the green sheet 50 is preferably in a range of0.1 to 5 mm.

[0138] Next, the conductor containing paste which is to serve as theelectrostatic electrode layer or the resistance heating element isprinted on the green sheet 50.

[0139] The printing is performed, in consideration of the shrinking rateof the green sheet 50, so that a desirable aspect ratio is obtained. Asa result, the electrostatic electrode layer printed body 51 and theresistance heating element layer printed body 52 are obtained.

[0140] The printed body is formed by printing the conductor containingpaste which contains conductive ceramic, metal particles and the like onthe green sheet.

[0141] As the conductive ceramic particles contained in the conductorcontaining paste, a carbide of tungsten or molybdenum is the mostpreferable because such a carbide is less likely to be oxidized and theheat conductivity thereof is less likely to drop, as compared with othermaterials.

[0142] Examples of the metal particle include particles of tungsten,molybdenum, platinum, nickel and the like.

[0143] The average particle diameter of the conductive ceramic particlesand the metal particles is preferably in a range of 0.1 to 5 μm. If theparticle size is too large or small, it is difficult to effect printingwith such a conductor containing paste.

[0144] As such a conductor containing paste used for the presentinvention, a conductor containing paste which is prepared by mixing: 85to 97 parts by weight of metal particles or conductive ceramicparticles; 1.5 to 10 parts by weight of at least one kind of binderselected from the group consisting of an acrylic binder, an ethylcellulose, a butyl cellosolve and polyvinyl alcohol; 1.5 to 10 parts byweight of at least one kind of solvent selected from α-terpineol,glycol, ethyl alcohol and butanol, is most preferably used.

[0145] The conductor containing paste is filled in holes formed bypunching and the like, whereby the conductor-filled through hole printedbodies 53, 54 are obtained.

[0146] Next, as shown in FIG. 7(a), green sheets 50 having the printedbodies 51, 52, 53, 54 are laminated with the green sheet 50 having noprinted body thereon. Several of one of the green sheet(s) 50 with theabove-mentioned structure are/is laminated on the green sheet on whichthe electrostatic electrode layer printed body 51 has been formed. Thereason why the green sheet 50, which does not have the printed bodies atthe side on which the resistance heating element is formed, is laminatedas described above, is prevent the end surface of the conductor-filledthrough hole from exposing and being oxidized during firing when theresistance heating element is formed. If the firing is to be performed,when the resistance heating element is formed, in a state in which theend surface of the conductor-filled through hole is exposed, a metalsuch as nickel which is less likely to be oxidized needs to be providedtherein by spattering. More preferably, the end surface of theconductor-filled through hole may be covered by a gold braze of Au—Ni.

[0147] (2) Next, as shown in FIG. 7(b), the lamination is subjected toheating and pressurizing, whereby the green sheet and the conductorcontaining paste are sintered.

[0148] The heating temperature is preferably in a range of 1000 to 2000°C. The pressure for pressurizing is preferably within a range of 100 to200 kg/cm². Heating is performed and pressuring is conducted in aninactive gas atmosphere. As the inactive gas, argon, nitrogen and thelike may be used, for example. In this process, the conductor-filledthrough holes 16, 17, the chuck positive electrostatic layer 2, thechuck negative electrostatic layer 3, the resistance heating element 5and the like are formed.

[0149] (3) Next, as shown in FIG. 7(c), blind holes 13, 14 forconnecting external terminals are formed.

[0150] It is preferable that at least a portion of the inner walls ofthe blind holes 13, 14 are made conductive and the conductive innerwalls are connected to the chuck positive electrostatic layer 2, thechuck negative electrostatic layer 3, the resistance heating element 5and the like.

[0151] (4) Finally, as shown in FIG. 7(d), the external terminals 6, 18are provided to the blind holes 13, 14 by way of a brazing fillermaterial such as gold braze and the like. In addition, a bottomed hole12 may optionally be formed so that themocouple can be embedded therein.

[0152] As solder, alloys of silver-lead, lead-tin, bismuth-tin and thelike can be used. The thickness of the solder is preferably in a rangeof 0.1 to 50 μm. When the thickness of the solder is within this range,connection by the solder is reliably conducted in a sufficient manner.

[0153] In the above-mentioned example, the electrostatic chuck 101(refer to FIG. 1) has been described. In case that the electrostaticchuck 201 (refer to FIG. 4) is to be produced, a ceramic substratehaving an electrostatic electrode layer is first produced, the conductorcontaining paste is then printed on the bottom face of the ceramicsubstrate, firing is effected to form a resistance heating element 15,and thereafter a metal layer 150 is formed by electroless plating andthe like. In case that the electrostatic chuck 301 (refer to FIG. 5) isto be produced, a metal foil and a metal wire as the electrostaticelectrode and the resistance heating element are embedded in the ceramicpowder, at the time of filling the ceramic powder (granules) in a moldor the like and forming a formed body. The electrostatic chuck 301 canbe produced by sintering the obtained formed body.

[0154] Further, in case that the electrostatic chuck 401 (refer to FIG.6) is to be produced, a ceramic substrate having an electrostaticelectrode layer is produced and then a Peltier element is joined to theceramic substrate by way of a thermal spraying of metal layer and thelike.

[0155] Next, an electrostatic chuck according to the second aspect ofthe present invention will be described hereinafter.

[0156] The second aspect of the present invention is an electrostaticchuck comprising: a ceramic substrate equipped with a temperaturecontrolling means; an electrostatic electrode formed on the ceramicsubstrate; and a ceramic dielectric film provided on the electrostaticelectrode, wherein the ceramic substrate has a diameter exceeding 300 mmand a thickness of 20 mm or less.

[0157] FIGS. 1 to 10 schematically show one example of the embodimentaccording to the second aspect of the present invention.

[0158] The ceramic substrate which constitutes the electrostatic chuckaccording to the second aspect of the present invention has diameterexceeding 300 mm, so that the ceramic substrate can adapt to siliconwafers of larger size and reliably cope with the semiconductor wafers ofthe next generation.

[0159] The thickness of the above-mentioned ceramic substrate is set tobe 20 mm or less, and desirably 10 mm or less. This is to reduce theheat capacity of the ceramic substrate by the decrease in thickness ofthe ceramic substrate so as to cope with the enlargement of the size ofthe electrostatic chuck. In a case of a ceramic substrate whose diameterexceeding 300 mm, the area of the periphery is relatively large i.e.,the area of the portion at which the ceramic substrate is brought intocontact with an atmospheric gas such as air is relatively large, wherebythe temperature drops significantly at the peripheral portion of theceramic substrate. Therefore, in the present invention, the area of theportion at which the ceramic substrate is brought into contact with airis decreased by reducing the thickness of the ceramic substrate, so thatthe temperature dropping at the peripheral portion can be prevented.

[0160] As the structures of the ceramic substrate, the ceramicdielectric film, the resistance heating element, the thermocouple andthe like of the electrostatic chuck according to the second aspect ofthe present invention are basically the same as those of theelectrostatic chuck according to the first aspect of the presentinvention, the detailed description of the electrostatic chuck accordingto the second aspect of the present invention will be omitted.

[0161] Further, regarding the method of producing the electrostaticchuck of the second aspect of the present invention, the method isbasically the same as the method of producing the electrostatic chuck ofthe first aspect of the present invention, except that the diameter ofthe ceramic substrate is designed so as to exceed 300 mm and the ceramicdielectric film preferably contains oxygen in an amount of 0.1 to 20weight %. Therefore, the detailed description thereof will be omitted.

BEST MODE FOR CARRYING OUT THE PRESENT INVENTION

[0162] The present invention will be described further in detailhereinafter.

EXAMPLE 1 Production of the Electrostatic Chuck (Refer to FIG. 1)

[0163] (1) A paste was produced by mixing: 100 parts by weight ofaluminum nitride powder (manufactured by Tokuyama co., the averageparticle diameter: 1.1 μm); 4 parts by weight of yttria (the averageparticle diameter: 0.4 μm); 11.5 parts by weight of acrylic binder; 0.5parts by weight of a dispersant; and 53 parts by weight of alcoholcomprising 1-butanol and ethanol. By using the obtained paste andperforming the forming process according to the doctor blade method, agreen sheet having a thickness of 0.47 mm was obtained.

[0164] (2) Next, the green sheet was dried for five hours at 80° C.Thereafter, portions which were to serve as through holes through whichlifter pins for the semiconductor wafer are inserted, with a diameterthereof being 1.8 mm, 3.0 mm and 5.0 mm, respectively and portions whichwas to serve as a conductor-filled through hole for effecting connectionwith the external terminal, were formed by punching.

[0165] (3) A conductor containing paste A was prepared by mixing: 100parts by weight of tungsten carbide particles whose average particlediameter was 1 μm; 3.0 parts by weight of an acrylic binder; 3.5 partsby weight of α-terpineol solvent; and 0.3 parts by weight of adispersant.

[0166] A conductor containing paste B was prepared by mixing: 100 partsby weight of tungsten particles whose average particle diameter was 3μm; 1.9 parts by weight of an acrylic binder; 3.7 parts by weight ofα-terpineol solvent; and 0.2 parts by weight of a dispersant.

[0167] The conductor containing paste A was printed on the green sheetby screen printing, whereby a conductor containing paste layer wasformed. The printing pattern was the pattern of concentric circles.Further, a conductor containing paste layer, which had the pattern ofthe electrostatic electrodes as shown in FIG. 2, was formed by screenprinting on another green sheet.

[0168] Further, the conductor containing paste B was filled in thethrough hole for the conductor-filled through hole provided foreffecting connection to the external terminals.

[0169] The green sheet 50, which had been subjected to theabove-mentioned treatment, was further laminated with: 34 sheets of thegreen sheet 50 on which the tungsten paste had not been printed,provided at the upper side thereof (on the heating face thereof); and 13sheets of the green sheet 50 on which the tungsten paste had not beenprinted, provided at the lower side thereof. The green sheet 50 on whicha conductor containing paste layer had been printed in the pattern ofthe electrostatic electrodes was further laminated on the lamination. Agreen sheet 50 on which the tungsten paste had not been printed wasfurther laminated on the above-mentioned laminated structure. Theresulting structure was pressed for adhesion at 130° C. and at apressure of 80 kg/cm², whereby a lamination was formed (refer to FIG.7(a)).

[0170] (4) Next, the obtained lamination was degreased in nitrogen gasat 600° C. for 5 hours and then hot-pressed for 3 hours at 1890° C. andat a pressure of 150 kg/cm², whereby a plate-formed body of aluminumnitride having a thickness of 3 mm was obtained. This plate-formed bodyof aluminum nitride was cut out so as to have a disc-like shape having adiameter of 210 mm, whereby a plate-formed body of aluminum nitridehaving a resistance heating element 5 whose thickness was 6 μm and widthwas 10 mm, a chuck positive electrostatic layer 2 and a chuck negativeelectrostatic layer 3 (whose thickness was 10 μm, respectively) insidethereof was obtained (refer to FIG. 7(b)).

[0171] The thickness of the ceramic dielectric film was 500 μm.

[0172] (5) Next, the plate-formed body obtained in the above-mentioned(4) was ground by using a diamond grindstone. Thereafter, a mask was setthereon and a bottomed hole (diameter: 1.2 mm, depth: 2.0 mm) forembedding a thermocouple was formed on the surface thereof by theblasting treatment using SiC and the like.

[0173] (6) Further, blind holes 13, 14 were each formed by hollowing outa portion at which the conductor-filled through hole was formed (referto FIG. 7(c)) External terminals 6, 18 made of Kovar were connected tothe blind holes 13, 14, respectively, by using gold brazing of Ni-Au andheating and reflowing at 700 ° C. (refer to FIG. 7(d)).

[0174] It is preferable that the connection of the external terminals iseffected by a structure wherein the external terminal is supported bythe support of tungsten at three portions. The external terminals can bereliably connected to the bind holes in such a structure.

[0175] (7) Next, a plurality of thermocouples for controlling thetemperature was embedded in the bottomed hole, whereby the production ofthe electrostatic chuck having a resistance heating element wascompleted.

EXAMPLE 2 Production of an Electrostatic Chuck (Refer to FIG. 4)

[0176] (1) A paste was produced by mixing: 100 parts by weight ofaluminum nitride powder (manufactured by Tokuyama co., the averageparticle diameter: 1.1 μm); 4 parts by weight of yttria (the averageparticle diameter: 0.4 μm); 11.5 parts by weight of acrylic binder; 0.5parts by weight of a dispersant; and 53 parts by weight of alcoholcomprising 1-butanol and ethanol. By using the obtained paste andperforming the forming process according to the doctor blade method, agreen sheet having a thickness of 0.47 mm was obtained.

[0177] (2) Next, the green sheet was dried for five hours at 80° C.Thereafter, portions which were to serve as through holes through whichlifter pins for the semiconductor wafer are inserted, with a diameterthereof being 1.8 mm, 3.0 mm and 5.0 mm, respectively and a portionwhich was to serve as a conductor-filled through hole for effectingconnection with the external terminal, were formed by punching.

[0178] (3) A conductor containing paste A was prepared by mixing: 100parts by weight of tungsten carbide particles whose average particlediameter was 1 μm; 3.0 parts by weight of an acrylic binder; 3.5 partsby weight of α-terpineol solvent; and 0.3 parts by weight of adispersant.

[0179] A conductor containing paste B was prepared by mixing: 100 partsby weight of tungsten particles whose average particle diameter was 3μm; 1.9 parts by weight of an acrylic binder; 3.7 parts by weight ofα-terpineol solvent; and 0.2 parts by weight of a dispersant.

[0180] The conductor containing paste A was printed on the green sheetby screen printing, whereby a conductor containing paste layer which hada pattern of electrostatic electrodes as shown in FIG. 9 was formed onthe green sheet.

[0181] Further, the conductor containing paste B was filled in thethrough hole for the conductor-filled through hole provided foreffecting connection to the external terminals.

[0182] The green sheet 50 which had been subjected to theabove-mentioned treatment was laminated with 2 sheets of the green sheet50 on which the tungsten paste had not been printed, provided at theupper side thereof (on the heating face thereof) and 48 sheets of thegreen sheet 50 on which the tungsten paste had not been printed,provided at the lower side thereof. The resulting structure was pressedfor adhesion at 130° C. and at a pressure of 80 kg/cm², whereby alamination was formed.

[0183] (4) Next, the obtained lamination was degreased in nitrogen gasat 600° C. for 5 hours and then hot-pressed for 3 hours at 1890° C. andat a pressure of 150 kg/cm², whereby a plate-formed body of aluminumnitride having a thickness of 5 mm was obtained. This plate-formed bodyof aluminum nitride was cut out so as to have a disc-like shape having adiameter of 210 mm, whereby a plate-formed body of aluminum nitridehaving a chuck positive electrostatic layer 2 and a chuck negativeelectrostatic layer 3 whose thickness were 15 μm, respectively insidethereof was obtained. The thickness of the ceramic dielectric film was1000 μm.

[0184] (5) Next, a mask was set on the bottom face of the plate-formedbody obtained in the above-mentioned (4) and a concave portion (notshown) and the like for embedding a thermocouple was formed on thesurface by the blasting treatment using SiC and the like.

[0185] (6) Next, a conductor containing paste for forming a resistanceheating element was printed on the surface (the bottom face) opposite tothe wafer putting surface, whereby a printed body for a resistanceheating element 15 was formed. As the conductor containing paste,“SOLVEST PS603D” manufactured by Tokuriki Kagaku Kenkyujo, which is usedfor forming a plated through hole of a printed circuit board, wasemployed. This conductor containing paste was a silver-lead paste andcontained 7.5 parts by weight, per 100 parts by weight of silver, ofmetal oxides comprising lead oxide, zinc oxide, silica, boron oxide andalumina (the weight ratio thereof being 5/55/10/25/5). The averageparticle diameter of the silver particles was 4.5 μm and the shape ofthe silver particles was scaly.

[0186] (7) The plate-formed body on which the conductor containing pastehad been printed was heated and fired at 780° C., so that the silver andlead contained in the conductor containing paste were sintered and bakedon the ceramic substrate. The plate-formed body was immersed in anelectroless nickel plating bath containing an aqueous solution of nickelsulfate (30 g/L), boric acid (30 g/L), ammonium chloride (30 g/L) andRochelle salt (60 g/L), so that a nickel layer 150 of 1 μm thicknesswhose boron content was 1 weight % or less was deposited on the surfaceof the silver sintered body 15. Thereafter, the plate-formed body wassubjected to the annealing treatment at 120° C. for 3 hours.

[0187] The thickness of the resistance heating element composed of thesilver sintered body was 5 μm, the width thereof was 2.4 mm and thesheet resistivity was 7.7 mΩ/□.

[0188] (8) Next, a blind hole for exposing the conductor-filled throughhole 16 was formed in the ceramic substrate. An external terminal pinmade of Kovar was connected to the blind hole by using gold brazing ofNi—Au alloy (Au: 81.5 weight %, Ni: 18.4 weight % and impurities: 0.1weight %) and heating and reflowing at 970 ° C. Further, an externalterminal pin made of Kovar was formed at the resistance heating elementby way of solder (tin: 9/lead: 1).

[0189] (9) Next, a plurality of thermocouples for controlling thetemperature was embedded in the concave portion, whereby theelectrostatic chuck 201 was obtained.

[0190] (10) Next, the electrostatic chuck 201 was fitted in a supportingcase 41 made of stainless steel having a sectional shape as shown inFIG. 10 through a heat insulator 45 comprising ceramic fiber(manufactured by Ibiden co. under the trademark of “Ibiwool”). Thesupporting case 41 has a coolant outlet 42 of cooling gas, so that thetemperature of the electrostatic chuck 201 can be adjusted.

[0191] The resistance heating element 15 of the electrostatic chuck 201fitted in the supporting case 41 was energized in order to raise thetemperature of the electrostatic chuck and also, the coolant was flowedthrough the supporting case, so that the temperature of theelectrostatic chuck 201 was controlled. The temperature control was veryexcellently performed.

EXAMPLE 3 Production of the Electrostatic Chuck 301 (FIG. 5)

[0192] (1) Two electrodes having shapes shown in FIG. 8 were formed bypunching a tungsten foil having a thickness of 10 μm.

[0193] These two electrodes and tungsten wires were set in a mold,together with 100 parts by weight of aluminum nitride powder(manufactured by Tokuyama co., the average particle diameter: 1.1 μm)and 4 parts by weight of yttria (the average particle diameter: 0.4 μm),and were hot-pressed in nitrogen gas for 3 hours at 1890° C. and at apressure of 150 kg/cm², whereby a plate-formed body of aluminum nitridehaving a thickness of 10 mm was obtained. This plate-formed body ofaluminum nitride was cut out so as to have a disc-like shape having adiameter of 250 mm, whereby a disc-shaped plate formed body wasobtained. Here, the thickness of the electrostatic electrode layer was10 μm. The thickness of the ceramic dielectric film was 2000 μm.

[0194] (2) This plate formed body was subjected to the processing stepsof the above-mentioned (5) to (7) of example 1, whereby theelectrostatic chuck 301 was obtained.

EXAMPLE 4 Production of the Electrostatic Chuck 401 (FIG. 6)

[0195] By carrying out the processing steps of the above-mentioned (1)to (5) of example 2,a plate-formed body of aluminum nitride having athickness of 14 mm was obtained. Thereafter, nickel was thermal sprayedto the bottom face of the plate-shaped aluminum nitride and then alead-tellurium type Peltier element was joined thereto, whereby theelectrostatic chuck 401 was obtained.

[0196] The thickness of the ceramic dielectric film was 2500 μm.

COMPARATIVE EXAMPLES 1 TO 5

[0197] In each of comparative examples 1 to 4, an electrostatic chuckwas produced in a manner similar to that of examples 1 to 4,respectively, except that the thickness of the ceramic substrate was 25mm. Comparative example 5 was carried out in a manner similar to that ofexample 1, except that the diameter and the thickness of the ceramicsubstrate were 190 mm and 25 mm, respectively.

COMPARATIVE EXAMPLE 6

[0198] Comparative example 6 was carried out in a manner similar to thatof example 1, except that 2 parts by weight of yttria (the averageparticle diameter: 0.4 μm) was added.

COMPARATIVE EXAMPLE 7

[0199] Comparative example 7 was carried out in a manner similar to thatof example 1, except that the aluminum nitride powder as the rawmaterial was heated for 3 hours so that oxygen was introduced thereto.

EXAMPLE 5 Electrostatic Chuck

[0200] (1) A paste was produced by mixing: 10 parts by weight ofaluminum nitride powder (manufactured by Tokuyama co., the averageparticle diameter: 1.1 μm); 4 parts by weight of yttria (the averageparticle diameter: 0.4 μm); 11.5 parts by weight of acrylic binder; 0.5parts by weight of a dispersant; and 53 parts by weight of alcoholcomprising 1-butanol and ethanol. By using the obtained paste andperforming the forming process according to the doctor blade method, agreen sheet having a thickness of 0.47 mm was obtained.

[0201] (2) Next, the green sheet was dried for five hours at 80° C.Thereafter, portions which were to serve as through holes through whichlifter pins for the semiconductor wafer are inserted, with a diameterthereof being 1.8 mm, 3.0 mm and 5.0 mm, respectively and a portionwhich was to serve as a conductor-filled through hole for effectingconnection with the external terminal, were formed by punching.

[0202] (3) A conductor containing paste A was prepared by mixing: 100parts by weight of tungsten carbide particles whose average particlediameter was 1 μm; 3.0 parts by weight of an acrylic binder; 3.5 partsby weight of α-terpineol solvent; and 0.3 parts by weight of adispersant.

[0203] A conductor containing paste B was prepared by mixing: 100 partsby weight of tungsten particles whose average particle diameter was 3μm; 1.9 parts by weight of an acrylic binder; 3.7 parts by weight ofα-terpineol solvent; and 0.2 parts by weight of a dispersant.

[0204] The conductor containing paste A was printed on the green sheetby screen printing, whereby a conductor containing paste layer wasformed. The printing pattern was the pattern of concentric circles.Further, a conductor containing paste layer, which had the pattern ofthe electrostatic electrodes as shown in FIG. 2, was formed by screenprinting on another green sheet.

[0205] Further, the conductor containing paste B was filled in thethrough hole for the conductor-filled through hole provided foreffecting connection to the external terminals.

[0206] The green sheet 50, which had been subjected to theabove-mentioned treatment, was further laminated with:34 sheets of thegreen sheet 50 on which the tungsten paste had not been printed,provided at the upper side thereof (on the heating face thereof); and 13sheets of the green sheet 50 on which the tungsten paste had not beenprinted, provided at the lower side thereof. A green sheet 50, on whicha conductor containing paste layer had been printed in the pattern ofthe electrostatic electrodes, was further laminated on the laminatedstructure. A green sheet 50 on which the tungsten paste had not beenprinted was yet further laminated on the above-mentioned laminatedstructure. The resulting structure was pressed for adhesion at 130° C.and at a pressure of 80 kg/cm², whereby a lamination was formed (referto FIG. 7(a)).

[0207] (4) Next, the obtained lamination was degreased in nitrogen gasat 600° C. for 5 hours and then hot-pressed for 3 hours at 1890° C. andat a pressure of 150 kg/cm², whereby a plate-formed body of aluminumnitride having a thickness of 3 mm was obtained. This plate-formed bodyof aluminum nitride was cut out so as to have a disc-like shape having adiameter of 310 mm, whereby a plate-formed body of aluminum nitridehaving a resistance heating element 5 whose thickness was 6 μm and widthwas 10 mm, a chuck positive electrostatic layer 2 and a chuck negativeelectrostatic layer 3 (whose thickness was 10 μm, respectively) insidethereof was obtained (refer to FIG. 7(b)). The thickness of the ceramicdielectric film was 500 μm.

[0208] (5) Next, the plate-formed body obtained in the above-mentioned(4) was ground by using a diamond grindstone. Thereafter, a mask was setthereon and a bottomed hole (diameter: 1.2 mm, depth: 2.0 mm) forembedding a thermocouple was formed on the surface by the blastingtreatment using SiC and the like.

[0209] (6) Further, blind holes 13, 14 were each formed by hollowing outa portion at which the conductor-filled through hole was formed (referto FIG. 7(c)). External terminals 6, 18 made of Kovar were connected tothe blind holes 13, 14, respectively, by using gold brazing of Ni-Au andheating and reflowing at 700 ° C. (refer to FIG. 7(d)).

[0210] It is preferable that the connection of the external terminals iseffected by a structure wherein the external terminal is supported bythe support of tungsten at three portions. The external terminals can bereliably connected to the blind holes in such a structure.

[0211] (7) Next, a plurality of thermocouples for controlling thetemperature was embedded in the bottomed hole, whereby the production ofthe electrostatic chuck having a resistance heating element wascompleted.

EXAMPLE 6 Production of an Electrostatic Chuck (Refer to FIG. 4)

[0212] (1) A paste was produced by mixing: 100 parts by weight ofaluminum nitride powder (manufactured by Tokuyama co., the averageparticle diameter: 1.1 μm); 4 parts by weight of yttria (the averageparticle diameter: 0.4 μm); 11.5 parts by weight of acrylic binder; 0.5parts by weight of a dispersant; and 53 parts by weight of alcoholcomprising 1-butanol and ethanol. By using the obtained paste andperforming the forming process according to the doctor blade method, agreen sheet having a thickness of 0.47 mm was obtained.

[0213] (2) Next, the green sheet was dried for five hours at 80° C.Thereafter, portions which were to serve as through holes through whichlifter pins for the semiconductor wafer are inserted, with a diameterthereof being 1.8 mm, 3.0 mm and 5.0 mm, respectively and a portionwhich was to serve as a conductor-filled through hole for effectingconnection with the external terminal, were formed by punching.

[0214] (3) A conductor containing paste A was prepared by mixing: 100parts by weight of tungsten carbide particles whose average particlediameter was 1 μm; 3.0 parts by weight of an acrylic binder; 3.5 partsby weight of α-terpineol solvent; 0.3 parts by weight of a dispersant.

[0215] A conductor containing paste B was prepared by mixing: 100 partsby weight of tungsten particles whose average particle diameter was 3μm; 1.9 parts by weight of an acrylic binder; 3.7 parts by weight ofα-terpineol solvent; 0.2 parts by weight of a dispersant.

[0216] The conductor containing paste A was printed on the green sheetby screen printing, whereby a conductor containing paste layer which hada pattern of electrostatic electrodes as shown in FIG. 9 was formed onthe green sheet.

[0217] Further, the conductor containing paste B was filled in thethrough hole for the conductor-filled through hole provided foreffecting connection to the external terminals.

[0218] The green sheet 50 which had been subjected to theabove-mentioned treatment was laminated with 2 sheets of the green sheet50 on which the tungsten paste had not been printed, provided at theupper side thereof (on the heating face thereof) and 48 sheets of thegreen sheet 50 on which the tungsten paste had not been printed,provided at the lower side thereof. The resulting structure was pressedfor adhesion at 130° C. and at a pressure of 80 kg/cm², whereby alamination was formed.

[0219] (4) Next, the obtained lamination was degreased in nitrogen gasat 600° C. for 5 hours and then hot-pressed for 3 hours at 1890° C. andat a pressure of 150 kg/cm², whereby a plate-formed body of aluminumnitride having a thickness of 5 mm was obtained. This plate-formed bodyof aluminum nitride was cut out so as to have a disc-like shape having adiameter of 330 mm, whereby a plate-formed body of aluminum nitridehaving a chuck positive electrostatic layer 2 and a chuck negativeelectrostatic layer 3 whose thickness were 15 μm, respectively insidethereof was obtained. The thickness of the ceramic dielectric film was1000 μm.

[0220] (5) Next, a mask was set on the bottom face of the plate-formedbody obtained in the above-mentioned (4) and a concave portion (notshown) and the like for embedding a thermocouple was formed on thesurface by the blasting treatment using SiC and the like.

[0221] (6) Next, a conductor containing paste for forming a resistanceheating element was printed on the surface (the bottom face) opposite tothe wafer putting surface, whereby a printed body for a resistanceheating element 15 was formed. As the conductor containing paste,“SOLVEST PS603D” manufactured by Tokuriki Kagaku Kenkyujo, which is usedfor forming a plated through hole of a printed circuit board, wasemployed. The conductor containing paste was a silver-lead pastecontaining 7.5 parts by weight of a metal oxide with respect to 100parts by weight of silver. This conductor containing paste was asilver-lead paste and contained 7.5 parts by weight, per 100 parts byweight of silver, of metal oxides comprising lead oxide, zinc oxide,silica, boron oxide and alumina (the weight ratio thereof being5/55/10/25/5). The average particle diameter of the silver particles was4.5 μm and the shape of the silver particles was scaly.

[0222] (7) The plate-formed body on which the conductor containing pastehad been printed was heated and fired at 780° C., so that the silver andlead contained in the conductor containing paste were sintered and bakedon the ceramic substrate. The plate-formed body was immersed in anelectroless nickel plating bath containing an aqueous solution of nickelsulfate (30 g/L), boric acid (30 g/L), ammonium chloride (30 g/L) andRochelle salt (60 g/L), so that a nickel layer 150 of 1 μm thicknesswhose boron content was 1 weight % or less was deposited on the surfaceof the silver sintered body 15. Thereafter, the plate-formed body wassubjected to the annealing treatment at 120° C. for 3 hours.

[0223] The thickness of the resistance heating element composed of thesilver sintered body was 5 μm, the width thereof was 2.4 mm and thesheet resistivity was 7.7 mΩ/□.

[0224] (8) Next, a blind hole for exposing the conductor-filled throughhole 16 was formed in the ceramic substrate. An external terminal pinmade of Kovar was connected to the blind hole by using gold brazing ofNi—Au alloy (Au: 81.5 weight %, Ni: 18.4 weight % and impurities: 0.1weight %) and heating and reflowing at 970° C. Further, an externalterminal pin made of Kovar was formed at the resistance heating elementby way of solder (tin: 9/lead: 1).

[0225] (9) Next, a plurality of thermocouples for controlling thetemperature was embedded in the concave portion, whereby theelectrostatic chuck 201 was obtained.

[0226] (10) Next, the electrostatic chuck 201 was fitted in a supportingcase 41 made of stainless steel having a sectional shape as shown inFIG. 10 through a heat insulator 45 comprising ceramic fiber(manufactured by Ibiden co. under the trademark of “Ibiwool”). Thesupporting case 41 has a coolant outlet 42 of cooling gas, so that thetemperature of the electrostatic 201 can be adjusted.

[0227] The resistance heating element 15 of the electrostatic chuck 201fitted in the supporting case 41 was energized in order to raise thetemperature of the electrostatic chuck and, also the coolant was flowedthrough the supporting case, so that the temperature of theelectrostatic chuck 201 was controlled. The temperature control was veryexcellently performed.

EXAMPLE 7 Production of the Electrostatic Chuck 301 (FIG. 5)

[0228] (1) Two electrodes having shapes shown in FIG. 8 were formed bypunching a tungsten foil having a thickness of 10 μm.

[0229] These two electrodes and tungsten wires were set in a mold,together with 100 parts by weight of aluminum nitride powder(manufactured by Tokuyama co., the average particle diameter: 1.1 μm)and 4 parts by weight of yttria (the average particle diameter: 0.4 μm),and were hot-pressed in nitrogen gas for 3 hours at 1890° C. and at apressure of 150 kg/cm², whereby a plate-formed body of aluminum nitridehaving a thickness of 10 mm was obtained. This plate-formed body ofaluminum nitride was cut out so as to have a disc-like shape having adiameter of 350 mm, whereby a disc-shaped plate formed body wasobtained. Here, the thickness of the electrostatic electrode layer was10 μm.

[0230] The thickness of the ceramic dielectric film was 2000 μm.

[0231] (2) This plate formed body was subjected to the processing stepsof the above-mentioned (5) to (7) of example 1, whereby theelectrostatic chuck 301 was obtained.

EXAMPLE 8 Production of the Electrostatic Chuck 401 (FIG. 6)

[0232] By carrying out the processing steps of the above-mentioned (1)to (5) of example 6, a plate-formed body of aluminum nitride having adiameter of 350 mm and thickness of 18 mm was obtained. Thereafter,nickel was thermal sprayed to the bottom face of the plate-shapedaluminum nitride and then a lead-tellurium based Peltier element wasjoined thereto, whereby the electrostatic chuck 401 was obtained. Thethickness of the ceramic dielectric film was 2500 μm.

COMPARATIVE EXAMPLES 8 TO 11

[0233] In each of comparative examples 8 to 11, an electrostatic chuckwas produced in a manner similar to that of examples 5 to 8,respectively, except that the thickness of the ceramic substrate was 25mm. In each of comparative examples 8 to 11, the thickness of theceramic dielectric film was 500 μm.

COMPARATIVE EXAMPLE 12

[0234] Comparative example 12 was carried out in a manner similar tothat of example 1, except that 2 parts by weight of yttria (the averageparticle diameter: 0.4 μm) was added.

COMPARATIVE EXAMPLE 13

[0235] Comparative example 13 was carried out in a manner similar tothat of example 1, except that the aluminum nitride powder as the rawmaterial was heated for 3 hours so that oxygen was introduced thereto.

COMPARATIVE EXAMPLE 14

[0236] Comparative example 14 was carried out in a manner similar tothat of example 1, except that the thickness of the ceramic dielectricfilm was made to 10 μm by grinding.

COMPARATIVE EXAMPLE 15

[0237] Comparative example 15 was carried out in a manner similar tothat of example 1, except that the thickness of the ceramic dielectricfilm was made to 5500 μm.

[0238] The electrostatic chucks of examples 1 to 8 and comparativeexamples 1 to 15, obtained by the above-mentioned processes, wereevaluated according to the parameters described below. The results areshown in Table 1.

[0239] Methods for Evaluation

[0240] (1) Temperature Rising Time and Temperature Dropping Time of theElectrostatic Chuck

[0241] Each of the electrostatic chucks according to the examples andcomparative examples was energized and the time required for thetemperature of the electrostatic chuck to rise to 400° C. was measured.The time required for the temperature of the electrostatic chuck tonaturally drop from 400° C. to 50° C. was also measured.

[0242] (2) Difference in Temperature on the Heating Face

[0243] The difference in temperature between the highest temperature andthe lowest temperature on the heating face when the temperature settingwas 400° C. was measured by a thermoviewer (“IR162012-0012” manufacturedby Japan Datum co.) for each of the electrostatic chucks according tothe examples and comparative examples.

[0244] (3) The Oxygen Content in the Ceramic Dielectric Film

[0245] Samples were sintered in the same condition for the sinteredbodies according to the above-mentioned examples and comparativeexamples, respectively. Then, each sample was pulverized in a mortarmade of tungsten. 0.01 g of each pulverized sample was collected andanalyzed by using an oxygen/nitrogen determinator (TC-136 model, made byLECO company) in the condition in which the sample heating temperaturewas 2200° C. and the heating time was 30 seconds.

[0246] (4) Measurement of Dispersion in the Chucking Force of theSilicon Wafer

[0247] Each of the electrostatic chucks according to the examples andcomparative examples was energized in the state in which ten fractionalpieces of a silicon wafer (which pieces were obtained by dividing asilicon wafer into ten parts) were set thereon, so that the temperatureof the electrostatic chuck was raised to 400° C. The chucking force ofthe silicon wafer at each divided section was measured by a load cell,and the average value thereof was calculated. Further, the differencebetween the largest chucking force and the smallest chucking force wasdivided by the above-mentioned average, and the obtained value wasexpressed by percentage. Dia- Thick- Temperature Temperature Differencein Film Oxygen Dispersion of meter ness rising dropping time temperaturethickness content chucking force (mm) (mm) time (sec.) (min.) (° C.)(μm) (wt. %) (%) Example 1 210 3 190 6.3 4 500 1.6 1 Example 2 210 5 28010.2 4 1000 1.6 1 Example 3 250 10 560 23.3 8 2000 1.6 1.5 Example 4 21014 900 45 8 2500 1.6 1.5 Comparative example 1 210 25 2250 112.5 15 5001.6 4 Comparative example 2 210 25 2240 112 15 1000 1.6 4 Comparativeexample 3 250 25 2280 115 15 2000 1.6 4 Comparative example 4 210 252230 110 15 2500 1.6 4 Comparative example 5 190 25 1110 55 10 500 1.6 4Comparative example 6 210 3 190 6.3 10 500 0.08 3 Comparative example 7210 3 190 6.3 10 500 22 3 Example 5 310 3 200 7.5 4 500 1.6 1 Example 6330 5 290 11.2 4 1000 1.6 1 Example 7 350 10 580 24.5 6 2000 1.6 1.5Example 8 350 18 950 46 6 2500 1.6 1.5 Comparative example 8 310 25 2300114 15 500 1.6 4 Comparative example 9 330 25 2350 115 15 500 1.6 4Comparative example 10 350 25 2350 115 15 500 1.6 4 Comparative example11 350 25 2400 116 15 500 1.6 4 Comparative example 12 310 3 200 7.5 8500 0.08 2 Comparative example 13 310 3 200 7.5 8 500 22 2 Comparativeexample 14 310 3 200 7.5 8 10 1.6 2 Comparative example 15 310 3 200 7.58 5500 1.6 2

[0248] As shown in Table 1, the time required for the temperature toreach 400° C. was 190 to 950 seconds in the electrostatic chucksaccording to examples 1 to 8, while the time required for thetemperature to reach 400° C. was much longer in the electrostatic chucksaccording to comparative examples 1 to 5 and 8 to 11. The time requiredfor the temperature dropping was reduced to 24.5 seconds or less bysetting the thickness of the electrostatic chuck to 10 mm or less(examples 1 to 3, 5 to 7). Further the difference in temperature waskept within 4° C., which is ideal, by setting the thickness and theoxygen content of the electrostatic chuck to be 5 mm or less and 20weight % or less, respectively.

[0249] The property of chucking force and the like of the electrostaticchucks bear no problems in both of the examples and the comparativeexamples. The substrate whose diameter is 300 mm or more exhibited asignificant drop of the temperature at the peripheral portion thereofwhen the thickness of the electrostatic chuck exceeds 25 mm. Therefore,by adjusting the thickness of the electrostatic chuck in a range of 25mm or less, the dispersion of the temperature and the chucking force atthe heating face of the electrostatic chuck can be reduced. Further, byadjusting the thickness of the dielectric film and the oxygen content inthe dielectric film, the dispersion of the temperature and the chuckingforce on the heating face can be reduced.

INDUSTRIAL APPLICABILITY

[0250] As described above, the electrostatic chucks according to thefirst and the second aspect of the present invention do not have solarge heat capacity and exhibit excellent temperature rising/droppingproperty, in spite of the relatively large diameter size of the ceramicsubstrate thereof, since thickness of the electrostatic chucks has beenreduced. Further, since the electrostatic chuck device can be madelighter and thinner as a whole, not only transportation of the device ismade easy but also the space occupied by the device in the operationsuch as semiconductor production can be reduced.

1. An electrostatic chuck comprising: a ceramic substrate equipped witha temperature controlling means; an electrostatic electrode formed onsaid ceramic substrate; and a ceramic dielectric film provided on saidelectrostatic electrode, wherein: said ceramic substrate has a diameterexceeding 190 mm and a thickness of 20 mm or less; and said ceramicdielectric film contains oxygen in an amount of 0.1 to 20 weight %. 2.The electrostatic chuck according to claim 1, wherein a resistanceheating element is used as said temperature controlling means.
 3. Anelectrostatic chuck comprising: a ceramic substrate equipped with atemperature controlling means; an electrostatic electrode formed on saidceramic substrate; and a ceramic dielectric film provided on saidelectrostatic electrode, wherein said ceramic substrate has a diameterexceeding 300 mm and a thickness of 20 mm or less.
 4. The electrostaticchuck according to claim 3, wherein said ceramic dielectric filmcontains oxygen in an amount of 0.1 to 20 weight %.
 5. The electrostaticchuck according to claim 3 or 4, wherein a resistance heating element isused as said temperature controlling means.
 6. The electrostatic chuckaccording to any of claims 1 to 5, wherein the thickness of said ceramicdielectric film is in a range of 50 to 5000 μm.